Only a limited number of molecules with demonstrated therapeutic value can be transported through the skin via unassisted or passive transdermal drug delivery. The main barrier to transport of molecules through the skin is the stratum corneum (the outermost layer of the skin).
Devices including arrays of relatively small structures, sometimes referred to as microneedles or micro-pins, have been disclosed for use in connection with the delivery of therapeutic agents, vaccines and other substances through the skin and other surfaces. The devices are typically pressed against the skin to deliver molecules to a particular location. Microneedles of these devices pierce the stratum corneum upon contact, making a plurality of microscopic slits which serve as passageways through which molecules of active components can be delivered into the body. In delivering an active component, the microneedle device can be provided with a reservoir for temporarily retaining an active component in liquid form prior to delivering the active component through the stratum corneum. In some constructions, the microneedles can be hollow to provide a liquid flow path directly from the reservoir and through the microneedles to enable delivery of the therapeutic substance through the skin. In alternate constructions, active component(s) may be coated on the microneedle array and delivered directly through the skin after the stratum corneum has been punctured.
Microneedle arrays can be used in conjunction with an applicator device capable of being used a number of different times. The microneedle arrays are generally used once and then discarded.
Microneedles can be delivered using a patch that carries the microneedles. The patches are typically manufactured in a flat sheet-like configuration, carrying the microneedles. Patches may be temporarily attached to a disposable collar for an applicator device using, for example, an adhesive. The disposable collar may then be temporarily attached to the applicator using, for example, a mechanical snap-fit.
Patches, with or without a microneedles, can have fragile and sanitary characteristics. It is generally desired that the patch and array not be touched before application to a target site. This presents difficulties in storing and transporting patches to desired locations for eventual application. The patches may be stored along with the collars. However, the collars are large, and storage of disposable collars takes up excessive space and generates excessive waste.
Thus, the present invention provides an alternative microneedle patch and patch assembly.